Method for determining paracetamol in whole blood by chronoamperometry following enzymatic hydrolysis

A method is proposed for the determination of paracetamol in whole undiluted blood, based on the enzymatic hydrolysis of the drug to p-aminophenol, which is then measured by chronoamperometry at a glassy carbon electrode. Hydrolysis of the paracetamol prior to electro-oxidation is shown to alleviate problems that arise from high background currents in the whole blood and so ensures a good linear correlation (r greater than 0.99) between the current and the paracetamol concentration. Recovery experiments and comparison with a reference method based on spectrophotometry suggest that the electrochemical assay only measures that proportion of paracetamol that is not bound to serum albumin.